1. Field of the Invention
This invention pertains generally to solids fabrication processes, and more particularly to a feedthrough device for distributing gas entrained materials to a rotating head assembly, such as found within a solids fabrication system.
2. Description of the Background Art
Fabrication of three-dimensional solids is being performed within fabrication systems that build up a solid by layered fusing bits of material carried in a gas. One such system is a directed light fabrication (DLF) system. In a DLF system powders are injected into a moving beam of high power light, generally a laser light beam. The powders are typically metallic particles, however plastics and other fusible materials can be used. The powders are carried by a stream of gas, commonly argon, to the focal point of the laser beam wherein fusing of the material to the previous layer of material occurs. The gas provides a non-reactive carrier for the particles of the powder which are to be fused into a solid. In practice, the powder often gets injected non-uniformly about the beam resulting in a build-up of the fused powder material that is also of non-uniform structure. The flow of powder in the input feed lines may be adjusted to suit conditions required at the head, yet non-uniform injection may still occur. One contributing factor to the non-uniform injection of powders arises when the laser head and nozzles within a DLF system rotate. Conventionally, in order to accommodate head rotation, the input lines have been provided with an amount of slack in them. During rotational movements, the input lines are thereby subjected to a variety of movements which alter the distribution of gas entrained powder flow being emitted at the nozzles.
To achieve a uniform finished structure, therefore, it is important to reduce the disruptive gyrations of powder feed lines whereby increased uniformity of powder injection may occur. The rotary powder feed through apparatus in accordance with the present invention provides a coupling which satisfies the need to minimize feed line movements to the head, and overcomes additional deficiencies in current techniques for the coupling of gas entrained powder to a rotating head assembly.